Particle Formation

A Survey of IFPRI work in Formation and Assembly

Overview

The pre-competitive aspects of particle Formation and Assembly relate to both process understanding and product performance relations.

Processing includes unit operations that are directly capable of creating new particles, assembling particles having a composite structure, further assembling particles into other superstructure forms, and even reversibly dispersing particles from larger composites back into primary particles.Unit operations within the IFPRI remit include crystallization, binder agglomeration, atomization and spray-drying, extrusion, compaction, and dispersion.IFPRI has supported several process control projects in the Formation area, including crystallization and agglomeration.Within the new structure of IFPRI, control-focus projects will be organized in the Systems area.

Product focus areas include the structure-property relations, where a desired performance vector may be related to a set of properties.Structure-property relations link particle characteristics (size, shape, morphology, porosity and distributions thereof) with process variables that can be used to adjust and control the same.

Summary of work by IFPRI

Particle Formation has been a focus area of IFPRI since its inception, initially focusing on processes for making particles, and more recently expanding to include particle assemblies. Over this time, IFPRI has provided over 1 million USD in support of pre-competitive research in Formation and Assembly, much of which forms the foundational basis of current practice in selected focus areas including granulation (IFPRI projects are listed in the Appendix).

IFPRI has an extensive record of work in granulation, including binder agglomeration and spray drying of granules. Early work included seminal work in micro-level characterization of agglomeration with viscous binders, including modeling and experimental work elucidating the balance of inertial and viscous forces in fluidized bed agglomeration, later extended to other mechanical agglomeration systems. Structure control is a current focus in the agglomeration area, including an exploration into the use of additive manufacturing for precise structure control. Spray drying has included extensive work in atomization, including atomization of concentrated slurries, as well as drying kinetics in context of thermally-sensitive materials. The current focus in spray drying is toward more fundamental understanding of single-droplet drying at elevated temperature.

Conversely, it is of industrial interest to understand dispersion of agglomerates, where dispersion may be critical to an intermediate or end-use application of the material. Dispersion projects have focused on understanding the strength of agglomerates and their modes of rupture under various shear fields.

IFPRI’s work in aerosol formation, solvent precipitation and crystallization has several streams of focus. One area of focus is the short-range forces and solvent effects that govern nucleation and stabilization of fine particles in suspension. Another theme is size and shape control, using both intrinsic (e.g., gel-limited) and actively controlled processes. A current focus area is toward molecular assembly, using templates to control nucleation.

Forming operations with high compression pressure include extrusion and die compaction. In both cases, much focus has been given to the evolution of compacted structure as a function of process parameters and selected model materials. The output of these projects has been significant in application of modeling to related unit operations.

Appendix

Agglomeration of binder-particle systems; Tardos, Ennis and Pfeffer (City University of New York) 1990